These studies will determine whether extracorporeal perfusion systems coated with crosslinked albumin, polyurethane, silica-free silicone or polyacrylamide (hydrogel) can preserve platelet numbers and function during total cardiopulmonary bypass in monkeys. Since platelets adhere to the above 4 surfaces poorly, we will determine whether platelet deposition, aggregation, release and sequestration within the reticuloendothelial system are reduced during cardiopulmonary bypass. We will also determine whether platelet aggregates obstruct obstruct microcirculation or disagregate during bypass. Toxicity of these materials and the effect on oxygenator gas exchange will also be studied.